1. Field of the Invention
The present invention relates to color toners and an image forming method using the color toners. More particularly, the present invention relates to yellow, magenta, and cyan toners which are used for forming color images using electrophotography, and to an image forming method using the color toners and a non-contact heat fixing method.
2. Discussion of the Background
Image forming methods using electrophotography are well known. Various color toners for the image forming methods have been proposed. For example, Japanese Laid-Open Patent Publication No. 9-171268 discloses color toners including a cyan toner including β phthalocyanine, a magenta toner including Rhodamine 6G xanthenesilicomolybdate, a yellow toner including a benzidine type pigment, and a black toner including carbon black. Japanese Laid-Open Patent Publication No. 9-171269 discloses color toners including a cyan toner including β phthalocyanine, a magenta toner including monoazo Lithol Rubine, a yellow toner including a benzidine type pigment, and a black toner including carbon black. These color toners can produce red images having good tint, i.e., having good color reproducibility, however, the color tone of a bluish violet color image produced by them is not satisfactory.
Japanese Laid-Open Patent Publications Nos. 2-66562 and 3-107869 have disclosed quinacridone type pigments as a colorant for a magenta toner. The tint of bluish violet color images is good, however the toners have a drawback in that the color tone of a red image is not satisfactory.
In addition, a benzidine type yellow pigment, Pigment Yellow 17, is typically used for yellow toners because of having good tint and transparency, however, the light resistance (in particular the resistance to sunlight) of the pigment is not good. Therefore green color images which are a combination of the yellow pigment with a cyan toner are easily changed to bluish green when the green color images are exposed to light.
Thus, it is difficult to form color toner images having good color reproducibility (i.e., to form color toner images whose colors are well balanced). In particular, it is difficult to reproduce color images having a good combination of red color reproducibility and blue color reproducibility. These problems concerning color reproducibility are prominent in the color images which are fixed with a non-contact type heat fixing method using an oven and the like rather than a heat roller fixing method. In addition, the color toner images generally have poor light resistance as mentioned above.
Because of these reasons, a need exists for color toners which can produce color images having good color reproducibility. In particular, a need exists for color toners which can produce color images having a good combination of red color reproducibility and blue color reproducibility, and good light resistance even when used for non-contact heat fixing methods.